Adventures in Accuracy

[FractalAudio]

Does this imply that Cliff will swap out components in the amp if he finds they don’t match the schematic?

Old amps I typically have "refreshed" after purchasing. New tubes, recap, change any resistors that are out-of-spec, clean and tighten the tube sockets, etc. I only buy amps with the original transformers. I've blown two transformers but fortunately they were in reissues so it wasn't a big loss. They were replaced with Hammond equivalents (and I think they actually sound better now).

Drive pedals don't require refreshing. Mostly because I simply buy new ones but even used ones don't suffer the same component drift as amps because the components aren't under the same stress as in an amp (temperature and voltage).

 

[aens]

Lol! I kept looking at the first graph on my phone n scratching my head thinking - "what's he talking about, there's only 2 lines here - where's the FAS/Klon comparison?!". Now, a day later I enlarge the image and see that the lines are right on top of one another!

Same here. Funny thing was I even read your post while watching tv and just kept reading the thread. Shortly after I also realized to zoom in the pictures. Oh I see, so this is what all of you are talking about…

 

[SwirlyMaple]

Here's another:

This is a Deluxe Reverb vs. the Axe-Fx:
View attachment 130158

And here's the other modeler vs. the amp:
View attachment 130161

Green and violet traces are the amp.

On the Axe-Fx I set the Speaker Impedance to LB-2 UK. Here's same test but using the Deluxe Reverb impedance curve:
The amp is still using the load box. You can see the impedance has a noticeable effect on the response but not that dramatic.
View attachment 130163

Is your “other modeler” the same modeler throughout all of these plots in this thread?

If so, I’m pretty sure it’s not the Helix. Guessing it’s the TMP.

 

[FractalAudio]

Is your “other modeler” the same modeler throughout all of these plots in this thread?

Yes.

It's not a Helix as I don't have one at the moment.

 

[Randalljax]

Here's another:

This is a Deluxe Reverb vs. the Axe-Fx:
View attachment 130158

And here's the other modeler vs. the amp:
View attachment 130161

Green and violet traces are the amp.

On the Axe-Fx I set the Speaker Impedance to LB-2 UK. Here's same test but using the Deluxe Reverb impedance curve:
The amp is still using the load box. You can see the impedance has a noticeable effect on the response but not that dramatic.
View attachment 130163

If this is the Fender well that’s just super embarrassing

 

[SwirlyMaple]

Here's another:

This is a Deluxe Reverb vs. the Axe-Fx:
View attachment 130158

And here's the other modeler vs. the amp:
View attachment 130161

Green and violet traces are the amp.

On the Axe-Fx I set the Speaker Impedance to LB-2 UK. Here's same test but using the Deluxe Reverb impedance curve:
The amp is still using the load box. You can see the impedance has a noticeable effect on the response but not that dramatic.
View attachment 130163

Another question if you don’t mind: what’s the source of these little peaks in the real amp? Some kind of resonance? Just curious since the Axe-Fx doesn’t have them and they are fairly abrupt.

 

[unix-guy]

Another question if you don’t mind: what’s the source of these little peaks in the real amp? Some kind of resonance? Just curious since the Axe-Fx doesn’t have them and they are fairly abrupt.

View attachment 130170

Just a guess but the first one is right at 60Hz... maybe noise from power?

 

[IronSean]

I'm sure he's had to change some physical components at times because he buys amps from various places and the odds are not good that all of them were working perfectly, but it doesn't make sense that it's necessary to do it on every amp that's modeled. For instance, when he was modeling the Carol Ann amps he was working closely with Alan Phillips and probably had perfect amps to compare to. Conversely, the other day he said he accidentally blew up two transformers when modeling amps so I expect he replaced those. So it's not implying that every amp modeled has had physical components changed.

When he has the schematic he can set the values for the modeled components to what the schematic says they should be instead of what they might measure as, then begin measuring the output of the different stages in the target amp and comparing those to the output of the modeler's stages. His methodology probably changes depending on the particular amp and whether he has the schematic and whether he wants the amp modeled so badly that he'll do it without the schematic. He's been doing this stuff a long time so he's probably done about everything that was required to get an amp into modeling condition.

"Amp block" in the Wiki talks about how he models and issues he's encountered, especially the changes that occur in manufacturing.

Note some amp schematics have deliberate "mistakes" in them to make it harder for their designs to be stolen, or easier to track who leaked the schematic, or many other reasons. So probably wouldn't be the best idea to modify a real amp to the schematic in all cases.

 

[Smittefar]

Here's another:

This is a Deluxe Reverb vs. the Axe-Fx:
View attachment 130158

And here's the other modeler vs. the amp:
View attachment 130161

Green and violet traces are the amp.

On the Axe-Fx I set the Speaker Impedance to LB-2 UK. Here's same test but using the Deluxe Reverb impedance curve:
The amp is still using the load box. You can see the impedance has a noticeable effect on the response but not that dramatic.
View attachment 130163

How different would two deluxe reverb amps (nominally the same amp of course) measure?

 

[FractalAudio]

Another question if you don’t mind: what’s the source of these little peaks in the real amp? Some kind of resonance? Just curious since the Axe-Fx doesn’t have them and they are fairly abrupt.

View attachment 130170

60 Hz hum.

 

[frankenbeans]

Old amps I typically have "refreshed" after purchasing. New tubes, recap, change any resistors that are out-of-spec, clean and tighten the tube sockets, etc.

Huh. I didn’t know that was part of your process. That’s really cool. Thanks!

 

[FractalAudio]

How different would two deluxe reverb amps (nominally the same amp of course) measure?

Not more than 1 dB. Usually less. Certainly not 5-10 dB.

 

[Rogerthat]

"but y no profilur yet?"

 

[unix-guy]

"but y no profilur yet?"

You already have the best... Why do you want something less accurate?

 

[Rogerthat]

You already have the best... Why do you want something less accurate?

Need more aliasing

 

[unix-guy]

Need more aliasing

Obviously my sarcasm detector needs calibration

 

[randocaster]

Yes.

It's not a Helix as I don't have one at the moment.

maybe Santa; ah, I mean The Grinch, will bring you one for Christmas

Eh, Line6 are a cool company who respect their customers IMO. No need to do that to them.

 

[sprint]

Eh, Line6 are a cool company who respect their customers IMO. No need to do that to them.

Was not meant to be disparaging - just an attempt (failed one obviously) at sarcastic humor along the lines of a company rep not likely wanting a competing product from Santa - anyway, clearly went over like a lead balloon, so post deleted.

 

[randocaster]

Was not meant to be disparaging - just an attempt (failed one obviously) at sarcastic humor along the lines of a company rep not likely wanting a competing product from Santa - anyway, clearly went over like a lead balloon, so post deleted.

FWIW I didn't take it in a negative way at all. I was also just making a joke.
Happy Thanksgiving! (if that's a thing for you).

 

[jaycal6]

Dumb question. These graphs show frequency response, right? Like running pink noise into the amp and Fractal? I would imagine that’s just one part of the accuracy equation? It doesn’t tell you anything about the attack of the note, sag, “feel,” etc.